For connecting one mechanical component part to another mechanical component part, it has been a popular practice to use a positioning pin called “dowel pin” or “knock pin”, as disclosed for example in Japanese Patent Application Laid-Open Publication No. HEI-3-170235 (hereinafter referred to as “the relevant patent literature”).
FIG. 14 hereof is a view explanatory of a fundamental overall construction of a conventionally-known technique disclosed in the relevant patent literature. An engaging groove 102 is formed in one end portion of a workpiece in the form of a cam shaft 100 having a plurality of cams 101 provided thereon, and a center hole 103, a female threaded portion 104 and a pin hole 105 are formed in advance in another end portion of the cam shaft 100. A positioning pin 106 is press-fitted into the pin hole 105 by means of a pin press-fitting device 107 through the following steps.
Namely, first, the cam shaft 100 is set on a workpiece positioning apparatus by a locking claw 108 of a workpiece position apparatus being brought into engagement with the engaging groove 102. Then, a rotation shaft 109 of the workpiece positioning apparatus is rotated to align the pin hole 105 with the center of the pin press-fitting device 107; namely, the phases of the pin hole 105 and the pin press-fitting device 107 are matched. The pin press-fitting device 107 is operated to press-fit the positioning pin 106 into the pin hole 105. After that, a timing pulley 111 depicted by imaginary line is brought into contact with the other end of the cam shaft 100 while being aligned with the positioning pin 106 and a bolt 112 is screwed into the female threaded portion 104, so that the timing pulley 111 is fixed to the cam shaft 100. The timing pulley 111 is positioned relative to the cam shaft 100 by means of the positioning pin 106, so that predetermined phase relationship between the cams 101 and the timing pulley 111 can be maintained.
However, wobbles would undesirably occur due to a gap unavoidably left between the engaging groove 102 and the engaging claw 108. Because amounts of rotations of the rotation shaft 109 and the cam shaft 100 would differ due to the wobbles, it tends to be difficult to control the amounts of rotations.
Further, in case the press-fitting of the pin failed, it is necessary to find out what or where the problem is. However, there are a multiplicity of defect or inconvenience factors to be checked, such as wobbles but also a positional error of the engaging groove 102 relative to the pin hole 105 and an adjustment error of the positioning apparatus, and one inconvenience factor would influence another or others. Thus, it would be very difficult to find out a cause of the problem. As a consequence, a great number of steps would be required for addressing the problem, which could result in a long time of product line stoppage.
Further, because the phase of the engaging groove 102 relative to the pin hole 105 differs among models for design conveniences, there is a need to provide a separate press-fitting station per model of workpiece, and thus, necessary facilities would become large in size. Furthermore, because a space for installing additional press-fitting stations has to be secured in preparation of future addition of models of workpieces, which would even further increase a size of necessary facilities.
Because it is necessary to enhance a production efficiency, there has been a demand for a more sophisticated workpiece positioning apparatus which is capable of readily controlling an amount of rotation of the workpiece and easily taking an effective measure against an inconvenience.